#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

int fib(int n)
{
    if (n <= 2)
    {
        return n;
    }
    else
    {
        int count = fib(n - 1) + fib(n - 2);
        return count;
    }
}
int main()
{
    int n = 0;
    scanf("%d", &n);
    int ret = fib(n);
    printf("%d\n", ret);
    return 0;
}